Gear case assembly

ABSTRACT

A gear case assembly includes an upper gear case and a lower gear case accommodating a drive axle, at least one rotation axle receiving power from the drive axle, and a power transmission unit for transmitting the power to the at least one rotation axis. The upper and lower gear cases are horizontally divided, and upper and a lower shrouds are integrally formed on the upper and lower gear cases proximate to ends of the rotation axis. The upper and lower shrouds form a surface for guiding a fluid that flows from an impeller connected to the rotation axle, and are horizontally divided. Scroll cases mounted on the upper and lower gear cases, together with the upper and lower shrouds, define a path for guiding the fluid that flows from the impeller. A common plane divides the upper and lower gear cases, and also divides the upper and lower shrouds.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This application claims the benefit of Korean Patent Application No. 10-2007-0031965, filed on Mar. 30, 2007, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a gear case assembly, and more particularly, to a gear case assembly that accommodates a rotation body used for a turbo compressor, a centrifugal compressor, or another mechanical device that increases the pressure of a gas by reducing its volume.

2. Description of the Related Art

A rotation body, such as an impeller on an axle, may be installed in a compressor, a blower, a turbo charger, or a marine engine. In order to drive the rotation body, a power transmission unit is accommodated in a gear case assembly to transmit power from a drive source to the impeller. Alternatively, a rotation body such as a turbine on an axle may be installed in an expander or another mechanical device that extracts energy from a fluid flow, and may provide a drive source from which power may be transmitted via a gear case assembly.

A known gear case assembly includes a gear case divided into, for example, an upper gear case and a lower gear case for supporting the rotation body and the power transmission unit therein. A shroud may be integrally formed on the gear case. The shroud defines a surface for guiding a fluid that flows from an impeller, and includes a roughly circular shape around a central bore. For example, a circular shroud is formed on a front portion of the lower gear case and protrudes toward the upper gear case.

According to the known gear case assembly, the rotation body includes an impeller disposed on an axle and driven by a drive source via the power transmission unit. The impeller is mounted at an end of the axle and has a diameter greater than that of the axle. The axle is accommodated in the gear case assembly, and the impeller is disposed outside the shroud of the gear case assembly. In order to accommodate the axle in the gear case assembly, a bore is formed in the gear case through the shroud.

However, when the impeller is preassembled to the axle, such a rotation body assembly cannot be mounted on the lower gear case as a whole since the diameter of the bore of the shroud is frequently less than the diameter of the impeller. Thus, the impeller must be disassembled from the axle in order to insert the rotation body assembly through the bore in the shroud of the lower gear case of the gear case assembly. Thereafter, a seal must be interposed between the gear case assembly and the rotation body assembly to prevent a leak from occurring therebetween.

However, before installing the rotation body assembly, a balancing operation is performed on the rotation body assembly before being disassembled. After installing the axle, the impeller is reassembled on the axle. As a result, the rotation body assembly may be out of balance due to the disassembling and reassembling of the rotation body assembly after the balancing operation is performed.

Also, in order to insert the rotation body assembly in the bore of a known gear case assembly, the bore must be of sufficient size in order to prevent interference between the elongated rotation body assembly and the gear case. Therefore, a seal holder needs to be additionally interposed between the rotation body assembly and the bore of the gear case and, as a result, the number of components increases, the assembly process becomes more complicated, and production costs also increase. Additionally, it is difficult to cast the gear case having the protruding shroud at the front portion of the lower gear case and it is also hard to perform a milling process, such as a cutting process or a finishing process, on the lower gear case because of limited working space.

Furthermore, because a groove that is required for a sealing O-ring is difficult to form in the lower gear case, the groove that is required for the sealing O-ring must be formed in the upper gear case. However, it is disadvantageous to turn the upper gear case upside down to form the groove required for the sealing O-ring.

SUMMARY OF THE INVENTION

The present invention provides a gear case assembly that simplifies the assembly process, has improved efficiency in terms of repair and maintenance, and has a reduced number of components.

In accordance with an aspect of the present invention, there is provided a gear case assembly including an upper gear case and a lower gear case accommodating a driving axis rotatably driven by a driving unit, at least one rotation axis receiving power from the driving axis and rotating, a power transmit unit for transmitting the power to the rotation axis, the upper gear case is horizontally divided from the lower gear case; an upper shroud and a lower shroud are integrally formed in end regions of the rotation axis of the upper and lower gear cases, respectively, to form a surface for guiding a fluid that flows from an impeller connected to the rotation axis, the upper shroud is horizontally divided from the lower shroud; and scroll cases are mounted in the end regions of the upper and lower gear cases opposite the upper and lower shrouds, respectively, to form a path for guiding the fluid that flows from the impeller together with the upper and lower shrouds. A bottom surface of the upper gear case is on the same level with a bottom surface of the upper shroud, and a top surface of the lower gear case is on the same level with a top surface of the lower shroud.

The upper gear case that is integrally formed with the upper shroud and the lower gear case that is integrally formed with the lower shroud using, for example, a bolt, and the bottom surface of the upper gear case may be on the same level with the top surface of the lower gear case.

Therefore, since a rotation axis assembly can be assembled to the gear case assembly without disjointing the impeller from the rotation axis assembly, an assembling process and repair and maintenance work can be facilitated, and the rotation axis assembly can be well balanced. Also, a milling process can be easily performed on the upper and lower gear cases at low cost since the bottom surface of the upper gear case and the top surface of the lower gear case are both plane. Furthermore, the upper and lower gear cases can be easily manufactures using a casting process.

A seal, for example, an O-ring, may be disposed between the top surface of the lower gear case, and the bottom surface of the upper gear case.

Since the top surface of the lower shroud is on the same level with the top surface of the lower gear case, a groove used for disposing the O-ring can be formed in the lower gear case. In this case, a surface of the lower gear case to be processed (i.e., the top surface of the lower gear surface) faces upward, so that it is unnecessary to turn the lower gear case upside down. Therefore, the groove used for disposing the O-ring can be easily processed in the top surface of the lower gear case that is combined with the bottom surface of the upper gear case.

A carbon seal may be interposed between the rotation axis and the upper and lower gear cases in a rear end region of the third impeller. In this case, it is unnecessary to enlarge a bore formed in the upper and lower gear cases to assemble the elongated rotation axis assembly unlike in the conventional case. Therefore, an additional component is not required to mount the carbon seal between the rotation axis and the upper and lower gear cases.

In accordance with another aspect of the present invention, there is provided a gear case assembly that includes a first gear case and a second gear case that accommodate a drive axle that is adapted to be rotatably driven by a driving unit, a first rotation axle that receives power from and is rotated by the drive axle, a power transmission unit that transmits the power from the drive axle to the first rotation axle, and a plane that divides the first and second gear cases. A first shroud and a second shroud are respectively integrally formed on the first and second gear cases and proximate a first end of the first rotation axle, the first and second shrouds form a first surface for guiding a fluid that flows from a first impeller disposed on the first rotation axle, the plane divides the first and second shrouds, and a first scroll case mounted on the first and second gear cases and proximate to the first and second shrouds, the first scroll case and the first surface define a path for guiding the fluid that flows from the first impeller. Wherein mating surfaces of the first and second gear cases coincide with the plane, and mating surfaces of the first and second shrouds coincide with the plane.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:

FIG. 1 is a front view of a gear case assembly used for a turbo compressor according to an embodiment of the present invention;

FIG. 2 is a plan view of a lower gear case assembly of the gear case assembly shown in FIG. 1, according to an embodiment of the present invention; and

FIG. 3 is a magnified view of region “A” of FIG. 2, according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be described more fully hereinafter with reference to the accompanying drawings, which show exemplary embodiments according to aspects of the invention.

FIG. 1 is a front view of a gear case assembly used for a turbo compressor according to an exemplary embodiment of the present invention, FIG. 2 is a plan view of a lower gear case assembly of the gear case assembly shown in FIG. 1, according to an exemplary embodiment of the present invention, and FIG. 3 is an enlarged view of region “A” of FIG. 2, according to an exemplary embodiment of the present invention.

Referring to FIGS. 1 through 3, the gear case assembly used for the turbo compressor according to an exemplary embodiment of the present invention includes an upper gear case 20, a lower gear case 10, first through third upper shrouds (only first and third upper shrouds 21 and 23 are shown in FIG. 1), first through third lower shrouds 11, 12, and 13, and first through third impellers 41, 42, and 43. The upper gear case 20 is horizontally divided from the lower gear case 10. The upper gear case 20 is combined with the lower gear case 10 such that a bottom surface of the upper gear case 20 is in contact with a top surface of the lower gear case 10, and the bottom surface of the upper gear case 20 forms a planar surface with the top surface of the lower gear case 10. A drive axle 30 and first and second rotation axles 31 and 32, are accommodated between the upper and lower gear cases 20 and 10.

The drive axle 30 is connected to a driving source, for example, a turbine (not shown), and rotatably driven thereby. For example, if the turbo compressor is driven by a gas turbine engine, the turbine rotates due to air heated by a combustor of the gas turbine engine and, in turn, the turbine drives the drive axle 30 of the turbo compressor.

The first rotation axle 31 and the second rotation axle 32 are disposed on the left and right sides of the drive axle 30, respectively. A power transmission unit, which transmits power from the drive axle 30 to the first and second rotation axles 31 and 32 includes a bull gear 33, a first pinion gear 34, and a second pinion gear 35. The bull gear 33 is mounted on the drive axle 30, the first pinion gear 34 is mounted on the first rotation axle 31, and the second pinion gear 35 is mounted on the second rotation axle 32. The bull gear 33 meshes with each of the first and second pinion gears 34 and 35.

The first impeller 41 is disposed at a front end of the first rotation axle 31, the second impeller 42 is disposed at a rear end of the first rotation axle 31, and the third impeller 43 is disposed at a front end of the second rotation axle 32. The first and second rotation axles 31 and 32 receive power from the drive axle 30 and rotate the first, second, and third impellers 41, 42, and 43.

Since the number of teeth and diameter of the first pinion gear 34 are smaller than those of the bull gear 33, the first rotation axle 31 rotates at a higher rate than the drive axle 30. Also, since the number of teeth and diameter of the second pinion gear 35 are smaller than those of the first pinion gear 34, the second rotation axle 32 rotates at a higher rate than the drive axle 30. Thus, air is compressed by the first impeller 41 in a first compression stage, the compressed air is further compressed by the second impeller 42 in a second compression stage, and the compressed air is further compressed by the third impeller 43 in a third compression stage. Hence, the turbo compressor according to the illustrated exemplary embodiment is a three-stage compressor. Although the gear case assembly used for the three-stage turbo compressor is exemplarily illustrated and described in the present embodiment, the present invention is not limited thereto. The present invention may be applied to any gear case assembly including a rotation body, such as the third impeller 43 disposed on the second rotation axle 32, the lower and upper gear cases 10 and 20 accommodating the rotation body, and the third lower and third upper shrouds 13 and 23, which are respectively formed on the gear cases 10 and 20.

The first lower shroud 11 is formed in the lower gear case 10 proximate the front end of the first rotation axle 31. The first lower shroud 11 is horizontally divided from the first upper shroud 21 such that a top surface of the first lower shroud 11 forms a planar surface with the top surface of the lower gear case 10, and a bottom surface of the first upper shroud 21 forms a planar surface with the bottom surface of the upper gear case 20.

Similarly, the second lower shroud 12 is formed in the lower gear case 10 proximate the rear end of the first rotation axle 31. The second lower shroud 12 is horizontally divided from the second upper shroud (not shown). Also, the third lower shroud 13 is formed in the lower gear case 10 proximate the front end of the second rotation axle 32. The third lower shroud 13 is horizontally divided from the third upper shroud 23.

When the first upper shroud 21 is combined with the first lower shroud 11, a circular shroud surface having a central bore is formed. Fluid flow provided by the first impeller 41 due to rotation of the first rotation axle 31 is guided by the circular shroud surface 11 and 21.

The first through third upper shrouds 21, (not shown), and 23 and the upper gear case 20 are integrally formed by, for example, a casting process. Also, the first through third lower shrouds 11, 12, and 13 and the lower gear case 10 are integrally manufactured by, for example, a casting process. The upper gear case 20 including the first through third upper shrouds 21, (not shown), and 23 and the lower gear case 10 including the first through third lower shrouds 11, 12, and 13 may be secured together with a threaded faster such as a bolt, a bolt and nut, or another type of releasable fastener. For example, one or more bolts may pass through the upper gear case 20 and be fastened to a threaded portion of the lower gear case 10 in order to secure together the upper and lower gear cases 20 and 10.

Since the upper gear case 20 that is integrally formed with the first through third upper shrouds 21, (not shown), and 23 is horizontally divided from the lower gear case 10 that is integrally formed with the first through third lower shrouds 11, 12, and 13, it is not necessary to disassemble the impellers 41, 42, and 43 from the first and second rotation axles 31 and 32 in order to install the first and second rotation axles 31 and 32 in the gear case assembly. Thus, the gear case assembly can be easily assembled and, in terms of repair and maintenance, achieve improved efficiency. Additionally, preassembly and balancing of the first and second rotation axles 31 and 32 is provided such that disassembly is not required.

Also, a milling process can be easily performed on the lower and upper gear cases 10 and 20 at low cost since both the bottom surface of the upper gear case 20 and the lower gear case 10 are planar. Furthermore, the upper and lower gear cases 20 and 10 can be easily manufactured by a casting process.

In addition, since the upper gear case 20, which is integrally formed with the first through third upper shrouds 21, (not shown), and 23, is horizontally divided from the lower gear case 10, which is integrally formed with the first through third lower shrouds 11, 12, and 13, it is unnecessary to increase the size of bore portions 10 a and 20 a, which are respectively formed in the upper and lower gear cases 10 and 20, to install the rotation axles 31 and 32, as is the case in a known gear case assembly. Thus, referring to FIG. 3, it is only necessary to insert a carbon seal 51 between the first and second rotation axles 31 and 32 and the lower and upper gear cases 10 and 20 in a rear region of the third impeller 43. Unlike the known gear case assembly, a separate carbon seal holder is not required to mount the carbon seal 51. Therefore, the number of components can be reduced, the assembly costs can be reduced, and failures caused by additional steps of the assembling process can be eliminated. Hence, the carbon seal 51 functions to prevent the leakage of air compressed by the third impeller 43.

A seal (not shown) is disposed between the top surface of the lower gear case 10 and the bottom surface of the upper gear case 20. The seal may be an O-ring. To install the O-ring, a groove 10 b is formed in the top surface of the lower gear case 10, which mates with the bottom surface of the upper gear case 20.

In the known gear case assembly, since the entire shroud is integrally formed with the lower gear case 1 and protrudes upward from the lower gear case 1, a groove, such as the groove 10 b required for an O-ring, cannot be formed in the lower gear case 1. Thus, with the known gear case assembly, it becomes necessary to disadvantageously turn the upper gear case 20 upside down and handle the upper gear case 20 to form the groove required for the O-ring in the upper gear case 20. However, according to aspects of exemplary embodiments of the present embodiment, since top surfaces of the first through third lower shrouds 11, 12, and 13 are on the same plane with the top surface of the lower gear case 10, it is possible to form the groove 10 b in the lower gear case 10. In this case, since a surface of the lower gear case 10 that is to be processed (i.e., the top surface of the lower gear surface 10) faces upward, it is unnecessary to additionally handle, e.g., turn over, the lower gear case 10. In conclusion, the groove 10 b required for the O-ring can be easily processed.

Referring particularly to FIG. 2, a first scroll case 36 is mounted to the lower and upper gear cases 10 and 20 proximate to the front end of the first rotation axle 31, a second scroll case 37 is mounted to the lower and upper gear cases 10 and 20 proximate to the rear end of the first rotation axle 31, and a third scroll case 38 is mounted to the lower and upper gear cases 10 and 20 proximate to the front end region of the second rotation axle 32. As illustrated in FIG. 3, along with the third lower and upper shrouds 13 and 23, the third scroll case 38 defines a path that guides air compressed by the third impeller 43. Although not shown in the drawings, the third scroll case 38 may be mounted on the lower and upper gear cases 10 and 20 using, for example, bolts or other releasable fasteners.

Although a gear case assembly used for a turbo compressor according to the exemplary embodiments of the present invention has been explained, the present invention is not limited thereto. For example, a gear case assembly according to exemplary embodiments of the present invention can be applied to a blower, a turbo charger, an engine, and an expander. That is, any gear case assembly including a rotation body, such as the third impeller 43 disposed on the second rotation axle 32, the lower and upper gear cases 10 and 20 accommodating the rotation body, and any of the first through third lower shrouds 11, 12, and 13, and first through third upper shrouds 21, (not shown), and 23 formed in the lower and upper gear cases 10 and 20, may be within the scope of the present invention. In this case, a driving gear for driving the rotation body, such as the third impeller 43 disposed on the second rotation axle 32, may be a turbine, a motor, or an engine.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by one of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. 

1. A gear case assembly comprising: a first gear case and a second gear case accommodating a drive axle adapted to be rotatably driven by a driving unit, a first rotation axle receiving power from and being rotated by the drive axle, a power transmission unit for transmitting the power from the drive axle to the first rotation axle, and a plane dividing the first and second gear cases; a first shroud and a second shroud being respectively integrally formed on the first and second gear cases and proximate a first end of the first rotation axle, the first and second shrouds forming a first surface for guiding a fluid that flows from a first impeller disposed on the first rotation axle, and the plane dividing the first and second shrouds; and a first scroll case mounted on the first and second gear cases and proximate to the first and second shrouds, the first scroll case and the first surface defining a path for guiding the fluid that flows from the first impeller, wherein mating surfaces of the first and second gear cases coincide with the plane, and mating surfaces of the first and second shrouds coincide with the plane.
 2. The gear case assembly of claim 1, wherein of the first gear case that is integrally formed with the first shroud and the second gear case that is integrally formed with the second shroud are fastened together with a threaded fastener.
 3. The gear case assembly of claim 2, further comprising a seal disposed between the mating surfaces of the first and second gear cases.
 4. The gear case assembly of claim 3, wherein the seal comprises an O-ring.
 5. The gear case assembly of claim 1, further comprising a second rotation axle being disposed parallel to the drive axle, and the drive axle being disposed between the first rotation axle and the second rotation axle.
 6. The gear case assembly of claim 5, wherein the first impeller is disposed at one end of the first rotation axle, a second impeller is disposed at another end of the first rotation axle, a third impeller is disposed at one end of the second rotation axle, wherein the fluid compressed by the first impeller then flows into the second impeller and is compressed by the second impeller, and the fluid compressed by the second impeller then flows into the third impeller and is compressed by the third impeller, and wherein sets of the first and second shrouds are formed on the first and second cases, respectively, and each set of the first and second shrouds is disposed proximate to a corresponding end of the first and second rotation axles.
 7. The gear case assembly of claim 6, further comprising a bull gear disposed on the driving axle, a first pinion gear disposed on the first rotation axle, and a second pinion gear disposed on the second rotation axle, wherein the first pinion gear and the second pinion gear mesh with the bull gear.
 8. The gear case assembly of claim 1, wherein the driving unit is one selected from the group consisting of a turbine, a motor, and an engine.
 9. The gear case assembly of claim 1, further comprising a carbon seal disposed between the first rotation axle and the first and second gear cases. 